Coal processing

ABSTRACT

A METHOD OF HYDROGENATING COAL TO LIQUEFY AT LEAST A PORTION THEREOF WHEREIN A LIQUID REACTION MEDIUM IS EMPLOYED WHICH CONTAINS A SUBSTANTIAL AMOUNT OF LIQUID WATER AND THE METHOD IS CARRIED OUT AT AN ELEVATED TEMPERATURE WHICH DOES NOT EXCEED 706*F.

United States Patent Int. Cl. Cg 1/06 US. Cl. 208-10 12 Claims ABSTRACT OF THE DISCLOSURE A method for hydrogenating coal to liquefy at least a portion thereof wherein a liquid reaction medium is employed which contains a substantial amount of liquid water and the method is carried out at an elevated temperature which does not exceed 706 F.

BACKGROUND OF THE INVENTION Heretofore normally solid, subdivided coal has been converted into a mixture of gaseous hydrocarbonaceous and liquid hydrocarbonaceous products by subjecting the coal to hydrogenation conditions under elevated temperatures and pressures in the presence of a hydrocarbonaceous liquid medium which is sometimes referred to by those skilled in the art as solvent.

A particularly useful coal liquefaction process, although not the only coal liquefaction process applicable to this invention is fully and completely disclosed in US. Pat. Re. 25,770, the disclosure of which is incorporated herein by reference. In this and other coal hydrogenation processes, the hydrogenation reaction medium is normally a hydrocarbonaceous liquid oil previously obtained from the liquefaction of solid coal, but can be other hydrocarbonaceous liquids such as Tetralin.

It has also been disclosed that very small, critical amounts of steam, when added to a coal liquefaction process employing a hydrocarbonaceous slurry medium, are of benfit to the conversion of solid coal to gaseous and liquid hydrocarbonaceous products. However, at the amount of steam and the operating conditions disclosed, the steam remains substantially completely in the vapor phase and does not provide a liquid medium with which coal is in contact while reacting.

SUMMARY OF THE INVENTION It has now been found that the use of relatively large amounts of liquid water as reaction medium in a coal liquefaction process can be beneficial to the operation of that process.

Accordingly, this invention relates to a method for hydrogenating normally solid coal in the presence of a liquid reaction medium wherein a substantial amount of the liquid medium is liquid water and the method is carried out at an elevated temperature which does not exceed 706 F.

Thus, this invention employs liquid water as a substantil portion of or as substantially the entire liquid medium for the coal liquefaction process. This invention is, therefore, carried out under conditions in which water will remain substantially in the liquid state so that the presence in the system of water vapor, steam, and the like, is minimized in favor of the presence of a liquid aqueous medium.

Accordingly, it is an object of this invention to provide a new and improved method for gasifying and/or liquefying normally solid coal. It is another object to provide a new and improved method for hydrogenating normally solid coal to at least partially liquefy same. It is another object to provide a method for employing an aqueous medium in a coal liquefaction and/ or gasification process.

3,745,108 Patented July 10, 1973 Other aspects, objects, and advantages of this invention will be apparent to those skilled in the art from this dis closure and the appended claims.

DETAILED DESCRIPTION OF THE INVENTION According to this invention, substantially any normally solid coal, e.g., semi-anthracite, bituminous, semi-bituminous, sub-bituminous, lignite, peat, and the like, can be used as the feed material to be at least partially liquefied and/or gasified. The coal is preferably subdivided in any conventional manner. Suitably subdivided coal is that in which at least about weight percent of the coal passes an 8 mesh (Tyler) sieve.

The subdivided coal is mixed with part or all of the liquid medium, subdivided catalyst if any inert contact particles if any, and molecular hydrogen and subjected to hydrogenation conditions for a time sufiicient such that at least part of the solid coal is converted to gaseous and/or liquid hydrocarbonaceous products. The amount remaining in the solid state is substantially unconverted coal, ash, char, coke, and the like.

In the method of this invention the liquid medium employed can comprise from about 25 weight percent to substantially weight percent of liquid water, the remainder of the liquid medium, if any being substantially hydrocarbonaceous. Thus, the method of this invention can employ as a medium substantially entirely liquid water or mixtures of liquid water with hydrocarbonaceous materials such as those taught by the prior art to be suitable medium materials.

It should be noted that the water which provides the reaction medium may be fresh, or may be recycled from the reaction eflluent. Since the loss of small amounts of water in the vapor phase is unavoidable in most cases, both fresh and recycled water are generally used to provide the medium. However in some cases, only fresh water is used. In all cases liquid water is fed to the inlet of the reactor. This water can be admixed with the coal or can be fed separately. A further possibility can be to mix the coal with a hydrocarbonaceous liquid and feed the water in separately. However, water comprises from about 25 to about 100 volume percent of the liquid which exists at the inlet of the reactor, and therefore a roughly corre sponding part of the liquid medium which exists within the body of the reactor (diluted to some extent by the liquid hydrocarbons formed in the reaction).

The hydrocarbonaceous liquid which can be mixed with the liquid water reaction medium is a mixture of materials and can have a boiling range of from the boiling temperature of butane to about 1500 F. and can contain one or more of: (a) naphtha, boiling in the range of from the boiling point of butane to about 400 F., (b) light distillate, boiling in the range of from about 400 to about 650 -F., (0) heavy distillate, boiling in the range of from about 650 to about 975 F., and, (d) residual fuel oil, boiling in the range of from about 975 F., to about 1500 F. The hydrocarbon part of the medium can be a liquid hydrocarbonaceous oil such as that produced by any coal liquefaction process, or any other liquid hydrocarbonaceous oil such as that obtained from Athabasca tar sands, shale, crude oil, and the like, or can be a hydrogen-donor hydrocarbonaceous liquid such as Tetralin, or aromatics such as anthracene, naphthalene, phenanthrene, and the like which have been partially or completely hydrogenated. Other hydrogen-donor mediums may be obtained by the hydrogenation of the hydrocarbonaceous liquid products obtained from the liquefaction of coal, and the like. The hydrogen-donor liquids can be useful for providing the hydrocarbonaceous part of the reaction medium but are optional from a hydrogenation point of view since often adequate hydrogenation can be obtained with molecular hydrogen alone.

The reaction liquid medium, be it entirely water or a mixture of water and hydrocarbonaceous liquids, is normally fed to the reactor with coal in a weight ratio of medium/coal of from about 0.1/1 to about 4/1 so that there is always substantial amounts of the liquid medium present in the hydrogenation operation.

The method of this invention is carried out under hydrogenation conditions including temperatures and pressures favorable to the hydrogenation of the coal, and under temperatures and pressures which favor the maintenance of the aqueous liquid medium substantially in the liquid state. The method of this invention is carried out at an elevated temperature which is not greater than 706 F., preferably at a temperature of from about 600 to 706 F., still more preferably at a temperature of from about 650 to 706 F. The total pressure on the system will also be elevated and should be greater than the vapor pressure of water at the elevated temperature of operation which will generally be at least about 1500 p.s.i.a., preferably from about 1545 to about 3226 p.s.i.a.

As will be shown hereinafter in the examples, a particularly significant advantage of the method of this invention is that it is substantially as effective at low hydrogen partial pressures as at high hydrogen partial pressures so that the beneficial results of this invention can be obtained using relatively low hydrogen partial pressures. Such an advantage is not normally obtainable with other coal liquefaction processes. Thus, in this invention hydrogen partial pressures not substantially greater than 1000 p.s.i.a. can be employed and favorable operating results still obtained.

The method of this invention can be carried out in the presence of one or more hydrogenation catalysts, one or more catalytically inert contact particles, combinations of one or more catalysts and one or more inert particles, or in the absence of catalysts or any inert particles externally supplied to the hydrogenation system.

Generally, if one or more catalysts are employed, any known hydrogenation catalyst can be used. Suitable catalysts include the metals, preferably in subdivided form such as powders, of iron, cobalt, nickel, vanadium, molybdenum, or tungsten, or compounds of these metals such as the halides, oxides, sulfides, molybdates, sulfates, or oxalates. Mixtures and other combinations of two or more of these metals and/or compounds of these metals can be employed as desired. Exemplary but nonlimiting materials that can be employed as hydrogenation catalysts include the chlorides of nickel, iron, and cobalt. There can also be used sulfates of iron, cobalt, and nickel, molybdates of cobalt, nickel, and iron, sulfides of tin, tungsten, molybdenum, or nickel, and combinations thereof, powders of metals such as nickel, cobalt, or iron. Oxides or combinations thereof can also be used as oxides of iron alone or in combination with nickel oxide, oxides of tungsten alone or in combination with nickel oxide, oxides of nickel, oxides of cobalt alone or in combination with nickel oxide, vanadium oxide, and the like.

The catalyst can be supported on a carrier material such as alumina, magnesia, silica, titania, zirconia, fullers earth, kieselguhr, clay such as kaolin (Kaolinite, Halloysite, Dickite, Nacrite, and Endellite) or bentonite (Montmorillonite, Beidellite, Nontronite, Hectorite, and Saponite), attapulgite, sepiolite, carbon, and the like. For example, combinations of iron oxide, alumina, and/or silica and/or titania can be employed. Also, oxides of molybdenum, oxides of tungsten, oxides of magnesium, sulfides of tungsten, and the like can be combined with alumina and/or silica and/or fullers earth, and the like. When carbon is employed as a support it can be in the form of wood char, coal char, activated carbon, or any other carbonaceous material containing a major amount of carbon.

In the above examples the iron, cobalt, and nickel can have valenc s f two or thre the vanadium a valence of five, four, three, or two, and the molybdenum and tungsten a valence of six, five, four, three, or two.

Each support material can be employed alone or in combination with other support materials and is used in an amount which supports any part or substantially all of the catalyst present.

The amount of catalyst used will be an effective hydrogenation catalytic amount. The catalyst is used in a catalyst/coal weight ratio of from about 0.005 1 to about 2/1, preferably from about 0.01/1 to about l/ 1.

Substantially any known inert (non-catalytic) contact particles can be employed in any desired combination with one another or with one or more catalyst particles. Suitable contact particles include subdivided refractory and/or inert materials such as sand, alpha-alumina, quartz, pumice, glass beads, silicon carbide, mullite, and the like. Alkalis such as calcium and magnesium oxides, or carbonates can also be employed. Various alkali or alkaline earth minerals such as limestone or dolomite are also useful as contact agents. Other solid materials which are included within the scope of inert contact particles for this invention include the unconverted coal, ash, char, coke, and the like which is present or formed in a coal liquefaction process and which can be recycled upstream in that process.

The inert contact particles are subdivided and are Preferably in the particle size range of from about 200 mesh (Tyler) to about A inch in largest cross-sectional dimension. The amount of these inert, non-catalytic particles employed will vary widely but generally will be from about 5 to about 70 weight percent.

This invention can also be carried out in the absence of any catalyst or externally supplied inert contact particles. The term externally supplied contact particles" is employed to distinguish from ash, char, coke, and the like which inherently build up internally of the coal liquefaction process. What is meant as externally supplied contact particles are materials (which can include ash, char, coke, and the like as well as sand, alumina, glass beads, etc.) which are deliberately added to the system from a source external to that system.

If desired, at least one metal salt and/or at least one acid which is either soluble or dispersible in the aqueous reaction medium of this invention can be employed in that medium in an amount efiective to increase the quantity of coal converted to liquid and/or gas. Suitable materials include inorganic metal salts and inorganic acids, particularly inorganic salts of an alkali metal or an alkaline earth metal, preferably lithium, sodium, potassium, rubidium, berryllium, magnesium, calcium, strontium, and barium, and inorganic acids such as hydrochloric, hydrobromic, hydrofluoric, hydriodic, sulfuric, phosphoric, and the like. Suitable anions for the inorganic salts include the halides, sulfate, sulfite, carbonate, phosphate, phosphite, hydroxide, etc. Organic acids such as the normal carboxylic acids can also be employed as well as the metal salts thereof as explained above. These salts and acids can be employed alone or in varying combinations of two or more thereof in widely varying amounts. The total amount used should be effective to increase the quantity of coal liquefied and/or gasified, but will generally be in the amount of from about 0.1 to about 50 weight percent based on the total weight of the reaction medium.

When a catalyst is employed which is soluble or dispersible in water it has been found advantageous to the overall reactions, as shown hereinafter in the examples, to impregnate the coal with the catalyst before hydrogenation.

In the following examples each run was carried out in a stirred autoclave using coal which was ground to pass a mesh (U.S.) sieve and to be retained on a 200 mesh (U.S.) sieve. All grinding and sizing was carried out under a nitrogen atmosphere. Demineralized water was em ployed and the water and coal were charged to the autoclave under a nitrogen atmosphere, after which the autoclave was sealed and purged three times with 500 p.s.i.g. nitrogen gas. Hydrogen under pressure was then added until the desired pressure level was reached after which heat was applied to the autoclave. Thereafter the stirrer was started and allowed to run until the reactor was cooled down after the run was completed. Residual gas was vented off through cold traps and into a gas holder. The autoclave was then opened and the water and products removed. The wet coal product was placed in a soxhlet extractor and extracted with benzene for about 24 hours. The excess benzene was removed from the extract and residue on a steam bath and then in a vacuum oven at 212 F. and 25 millimeters mercury. The asphaltene content of the extract was determined by precipitation with normal hexane. Other analytical data consisted of a mass spectrometer analysis of the residual gas from the autoclave and an elemental analysis of the product fractions. The product fractions were the gas in a weight percent based on the total weight of the coal charged as determined by the mass spectrometer analysis of residual gas at the end of the run, the oil which was all of the product that was soluble in both benzene and normal hexane, asphaltene which was all of the product that was soluble in benzene but insoluble in normal hexane, and insolubles which were all of the product that was not soluble in benzene. The insolubles can be defined as unconverted coal and used as the measure of coal conversion. Each of the runs were carried out at 650 F. and at a total pressure greater than 2200 p.s.i.g. (the vapor pressure of water at 650 F.) so that the liquid water initially charged to the autoclave was maintained substantially in the liquid state during the run and therefore functioned as liquid reaction medium rather than steam during the run.

EXAMPLE 1 In run 1, 90.5 parts by weight Pittsburgh #8 bituminous coal was mixed with 400 parts by weight of water. This mixture was soaked for 1 hour under a nitrogen atmosphere to allow good mixing of the components before contacting with hydrogen, and was then subjected to a hydrogen partial pressure of 800 p.s.i.g. at the 650 F. reaction temperature for 21 hours.

Run 2 was carried out in exactly the same manner as run 1 except that the 400 parts by weight of water had dissolved therein 1.8 parts by weight of ammonium molybdate [(NH Mo O -4I-I O],- which is a hydrogenation catalyst.

The results of runs 1 and 2 are set forth in Table 1.

TABLE 1 Run Gas, Wei ht percent-... Oil, weig It can be seen from the above runs 1 and 2 that the presence of the hydrogenation catalyst had little effect on the conversion or product mix so that this invention is equally useful whether a hydrogenation catalyst is or is not employed.

EXAMPLE 2 In run 3 Bruceton bituminous coal in the amount of 91.6 parts by weight was mixed with 400 parts by weight water having dissolved therein 1.8 parts by weight of ammonium molybdate as described in Example 1, the mixture soaked under a nitrogen atmosphere for 1 hour for good mixing and then reacted under 3800 p.s.i.g. hydrogen pressure at the reaction temperature for 21 hours.

Run 4 was carried out in exactly the same manner as run 3 except that the hydrogen partial pressure was 800 p.s.1.g.

The results of these runs are set forth in Table 2.

TABLE 2 Run 3 4 Gas, weight percent 4. 3 1. 7 Oil, weight percent. 14. 7 16.0 Percent carbon- 86. 9 87. 2 Percent hydrogen 8. 3 8. 8 Percent oxygen 3. 1 3. 3 Percent nitrogen- 1. 0 0. 9 Percent sulfur 0.2 0. 3 Asphaltene, weight percent... 21. 1 29. 8 Percent carbon... 86. 5 86. 7 Percent hydrogen 6. 9 6. 7 Percent oxygen- 4. 9 4. 9 Percent nitrogen. 1. 7 1. 2 Percent sulfur 0.0 O. 2 Insoluble, weight percent. 60.0 52. 5 Percent carbon 85. 4 84. 6 Percent hydrogen 6. 4 6. 6 Percent oxygen--. 5. 4 6. 3 Percent nitrogen- 1. 6 1. 7 Percent sulfur... l. 1 1. 8 Coal conversion, weight percent. 40. 0 47. 6

It can be seen from the above runs 3 and 4 that run 4 with its 800 p.s.i.g. hydrogen partial pressure had a good total conversion and product mix as compared to run 3 with its 3800 p.s.i.g. hydrogen partial pressure. This shows that the method of this invention is quite effective with hydrogen partial pressures not greater than 1000 p.s.i.a.

EXAMPLE 3 TABLE 3 Percent nitrogen- Percent sulfur Asphaltene, weight percent Percent carbon- Percent hydrog Percent oxygen--. Percent nitrogen. Percent sulfur Insoluble, weight percent- Percent carbon--. Percent hydrogen Percent sulfur Coal conversion, weight percent...-

1 Not obtained.

It can be seen from the above data that the addition of phosphoric acid in run 5 substantially increased the amount of coal converted.

EXAMPLE 4 In run 6, 91.2 parts by weight Bruceton bituminous coal was impregnated with 1.8 parts by weight ammonium molybdate (described in Example 1). The impregnated coal was mixed with 400 parts by weight water, and the mixture reacted at the reaction temperature under a hydrogen partial pressure of 4200 p.s.i.g. for 21 hours.

The coal was impregnated with the ammonium molybdate by soaking the coal in an aqueous solution of am- Run Gas, weight percent. 011, weight percent.

Percent carbon.-

Percent hydrogen- Percent oxygen-.-. Percent nitrogen- Percent sulfur Asphaltene, weight percent Percent carbon Percent hydrogen. Percent oxygen"--. Percent nitrogen Percent sulfur Insoluble, weight percent Percent carbon Percent hydroge Percent oxygen" Percent nitrogen Percent sulfur Coal conversion, weight percent.-.

1 N t obtained.

It can be seen from the above data that preimpregnation of the coal with catalyst improved the results of the method.

EXAMPLE Run 7 was carried out by mixing 88.8 parts by weight of Pittsburgh No. 8 bituminous coal with 100 parts by weight tetralin and 1.8 parts by weight ammonium molybdate (described in Example 1), and reacting the mixture under a hydrogen partial pressure of 1500 p.s.i.g. for 3 hours.

Run 8 was carried out by mixing 88.8 parts by weight Pittsburgh No. 8 bituminous coal with 100 parts by weight water, 300 parts by weight Tetralin and 1.8 parts by weight ammonium molybdate (described in Example 1), and reacting the mixture under a hydrogen partial pressure of 1775 p.s.i.g. for 3 hours.

The results of these two runs are set forth in Table 5.

TABLE 5 Coal conversion, weight perce 1 Not obtained.

Run 7 shows the results obtained when tetralin and no water was employed as a reaction medium. Run 8 8 shows that a mixture of weight percent Tetralin and 25 weight percent water was operable according to this invention.

Reasonable variations and modifications are possible within the scope of this disclosure without departing from the spirit and scope of this invention.

What is claimed is:

1. In a method for hydrogenating normally solid coal in the presence of an eifective dispersing amount of a liquid medium to liquefy at least a portion of said coal, the improvement comprising, said liquid medium contains at least about 25 weight percent liquid water based on the total weight of the liquid medium, the remainder, if any, of said liquid medium being substantially hydrocarbonaceous, said method being carried out at an elevated temperature not greater than 706 F. and the total pressure is greater than the vapor pressure of water at said elevated temperature so that said liquid water is maintained substantially in the liquid state during said hydrogenating method.

2. A method according to claim 1 wherein said liquid medium is composed substantially only of liquid water.

3. A method according to claim 1 wherein said elevated temperature is from about 600 to about 706 F.

4. A method according to claim 1 wherein the hydrogen partial pressure is not substantially greater than 1000 p.s.1.g.

5. A method according to claim 1 wherein said liquid medium contains one of at least one metal salt, at least one acid, and combinations thereof in an amount effective to increase the quantity of coal liquefied and/or gasified.

6. A method according to claim 5 wherein said liquid medium contains phosphoric acid.

7. A method according to claim 1 wherein said method is carried out in the presence of catalyst.

8. A method according to claim 1 wherein catalyst is employed and said coal is impregnated with said catalyst before hydrogenation.

9. A method according to claim 1 wherein said liquid medium is present in an amount such that the liquid medium/coal weight ratio which is fed to the reactor is in the range of from about 0.1/1 to about 4/1.

10. A method according to claim 1 wherein said method is carried out in the presence of catalytically inert particles.

11. A method according to claim 1 wherein said method is carried out in the presence of a combination of catalyst and catalytically inert particles.

12. A method according to claim 1 wherein said method is carried out in the absence of catalyst and externally supplied inert particles.

References Cited UNITED STATES PATENTS 2,191,156 2/1940 Pier et a1 208-10 3,488,280 1/ 1970 Schulman 208-10 3,502,564 3/1970 Hodgson 208--l0 OSCAR R. VERTIZ, Primary Examiner S. B. SHEAR, Assistant Examiner 

